Good point.
Is that more or less dystopian than the folks I've seen in India breaking stones with a hammer into small piles of gravel?
I get that none of it is necessary in a world which is over flowing with wealth except that it is locked up by the .1%. Do you think Marx or Lenin bought into a communist state where there even was a 1%? As an engineer you work with what you have, not with what you imagine could be, in the hope that you can move the situation forward into something that would be more to your general liking.
So yes, it would suck rocks if the only work you could find in a city was providing motive force for elevators when the power was out. The only thing that would suck worse than that would be that you could find no work at all in a city and were considering a life of crime to avoid starving.
The GP exposed a very wide price difference between apartments on the lower floors and the ones on the upper floors. So the problem statement (in isolation) was "recapture value of upper level apartments" and the reasoning there was that in developed countries upper floor apartments seem more valuable than lower floor ones.
The primary reason for this price discrepancy was power outages and then a non-functioning elevator.
So electricity generation is pretty well known, and the costs are modest, the questions are implementation vs environment.
Generators are available that run on a wide variety of fuels, unlike vehicles you can readily run them on gasoline, diesel, bio-diesel, alcohol, propane, or natural gas (methane).
As the use would be intermittent (assuming the power is available most of the time) any process that slowly accumulated fuel for the generators could be consumed during periods of need. If rationing petroleum products make them unusable collecting waste oil from restaurants to make bio diesel might be an option, or fermenting the trimmings from doing the lawn work for alcohol, or even capturing methane from a digester attached to the apartments very own sewer/septic system.
If electricity generation is simply off the table it is always possible to lift people mechanically. A good elevator/lift will be counter balanced so that with the operator it tends to rise "up" when the brake is removed, and 'down' when passengers are present. (note mechanically operated elevators need an operator). For "up" capacity without power you could hire a dozen people to pedal bicycle like transmissions attached to the elevator winch. Since we're serving the 1% here you can probably pay (on a temporary basis) a number of the 99% for 20 minute stints of pedalling, 40 minutes rest.
No one mentioned if the lower floors had power when power was out, if they don't and the only barrier to making the upper floors valuable is reliable lift service, that seems doable even in a very constrained environment. And if you recapture value so that a $200 apartment becomes a $20,000 apartment, that is a lot of value to recapture.